1. Field of the Invention
The present invention relates to a torsional vibration monitoring apparatus for monitoring torsional vibration occurring in a rotating shaft system such as for a power generator turbine, in which the torsional vibrations are measured at a small number of measurable certain positions on the rotating shaft system where the measurements are possible and stresses at other arbitrary positions thereon are estimated by linearly decomposing the measured vibrations, and the rotating shaft system is monitored on a fatigue life expenditure on the basis of the estimation obtained from the linear decomposition of the torsional vibration.
Furthermore, the present invention relates to a torsional vibration monitoring apparatus in which, when the torsional vibration whose stresses can not be estimated by the linear decomposition is produced, real torsional vibrations are recorded from which data may be obtained for other analysis.
2. Description of the Prior Art
It has been commonly recognized that, in designing a rotating shaft system such as turbine generator, compressor or marine diesel engine, it is important to exactly know various disturbances affecting the rotating shaft system. Particularly, it is very important for operators of the rotating shaft system to know a fatigue life expenditure of the rotating shaft system which may vary with the disturbance. Since, however, the length of the rotating shaft system of, for example, the turbine generator is generally very long and may become several tens meters in some cases, it is necessary to set a number of measuring positions along the rotating shaft system, causing a monitoring of the shaft system to be very difficult.
It is well known that torsional vibration occurring along the rotating shaft system must be measured because it may attribute to the fatigue and damages of the shaft system. However, it is disadvantageous economically to install torsional vibration measuring devices at a large number of positions on and along the rotating shaft system and it is sometimes impossible physically to do so.